Google is on a fresh collision course with users after it claimed that people
who use its Gmail service have “no legitimate expectation of privacy”.

The internet giant argued in a US lawsuit that people who send messages via email should not “be surprised” if those messages are intercepted by the recipient’s email provider, in the same way that someone sending a letter to a business associate might expect it to be opened by a secretary.

"People who use web-based email today cannot be surprised if their emails are processed,” Google said. “Indeed, 'a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties,” it added, citing a Supreme Court judgment handed down over electronic communications in 1979 – long before Google existed.

Google makes its money from targeting adverts at users based on detailed information about them, but it is rare that the California business is so clear about the deal people are entering when they use Google services, or even send messages to other people who do so.

The company is adamant that data privacy is of paramount importance, and spends a lot of time and money on cajoling regulators that users have myriad ways to opt out of sharing more information than they want.

It has also been battling to allay privacy fears after it was accused of handing user data over to America’s National Security Agency, in common with a number of major technology companies. Google claims it only supplied information where it was legally obliged to do so, and called on the US government to lift certain restrictions so that it could explain how many times it had handed over data.

However, the company made its stark claim about users’ legitimate expectations” in a 39-page document filed in San Jose, calling for the dismissal of a class-action lawsuit over so-called “data-mining” by Google.

The plaintiffs argue that by automatically scanning their emails, Google has engaged in illegal interception. Google scans messages in order to filter out unwanted “spam” emails, and to help it look for keywords so that it can target adverts more effectively.